The present invention relates to a sluice valve arrangement, and more particularly to a sluice valve arrangement of the type which is designed to open an opening through which a workpiece is fed into a vacuum chamber, or to air-tightly close the opening so as to treat the workpiece in the vacuum chamber in a hermetic state.
In the treatment of a workpiece under vacuum, for example, in the vacuum drying of workpieces or the vacuum brazing of metals, various sluice valve arrangements have been used to permit easy feeding of workpieces into vacuum chambers, and to provide hermetic closing of the openings through which the workpieces have been supplied into the vacuum chambers, thereby effectively keeping the vacuum chambers in an air-tight state. One typical example of the sluice vlave arrangements is designed to be opened or shut between a vacuum chamber and a pre-chamber put in communication therewith so as to reduce the amount of open air entering into the vacuum chamber as much as possible, in the case of supplying or discharging a workpiece into or out of the vacuum chamber.
Referring to FIG. 1, an opening or shutting sluice valve arrangement 4 (4') is disposed between a vacuum chamber 1 and a pre-chamber 2 (3) put in communication with the vacuum chamber 1.
With the arrangement of this type, the vacuum chamber is invariably maintained at a desired pressure. The sluice valve 4 (4') is hermetically closed to render the pressure in the pre-chamber 2 (3) substantially equal to that in the vacuum chamber 1, and then manipulated to put the prechamber 2 (3) in communication with the vacuum chamber 1, while the said pressure is maintained. Thereafter, feeding or discharging the workpiece into or out of the vacuum chamber 1 is effected.
The said sluice valve arrangement 4 (4') should have a passage of a greater sectional area because of the need of feeding the workpiece into both the vacuum chamber 1 and the pre-chamber 2 (3). With this arrangement, it is further required to reduce the interval between the flanges as much as possible so as to enable the workpiece to be delivered without using any delivery system in the arrangement.
This is the reason why use has heretofore been made of the sluice type valve arrangement employing a flat valve member, as will be understood from FIG. 2.
This sluice type valve arrangement is constructed from a valve box B including a passage F provided on its edge with flanges A and a flat valve member D disposed hermetically in a guide groove C in such a manner that it is vertically or horizontally slidable thereon. The passage F is opened and shut by the valve member D driven by a driving mechanism E. The valve box B includes a housing G designed to accommodate the valve member D when it is opened, and to maintain the passage F in a hermetic state. The housing G is kept under vacuum as mentioned above, and receives atmospheric pressure on its outer wall. To this end, the outer wall of the housing G should be of the structure sufficient to resist to atmospheric pressure, and is usually reinforced with a latticed material H, as illustrated.
When the said material is attached to the valve box B as by welding, however, there is a fear that it may suffer distortion and deformation due to heat.
When the passage F is shut by the valve member D, and the pre-exhaust chamber is expanded to atmospheric pressure, a load is applied on the valve member D. Due to its flatness, the valve member D may be distored by a vacuum load applied thereon, rendering its opening or shutting difficult and its hermetic closing more impossible. It has been found that as the diameter of the passage F increases, such problems are more likely to arise.